Optical waveguide devices, such as Mach-Zehnder coupler devices and long period fiber gratings, which are utilized with optical signals as transmitting filters, sensors, and wavelength multiplexing and demultiplexing devices provide good performance at standard room temperatures but exhibit thermal spectral shifts and related poor performance when used in environments where they are exposed to thermal variation and fluctuations in temperatures.
Mach-Zehnder coupler devices and long period fiber gratings can be used in narrow-band, multi-wavelength system applications as transmitting filters. In addition, Mach-Zehnder coupler devices can be used as sensors, and wavelength multiplexing and demultiplexing devices.
In a long period fiber grating a long period grating is formed in the fiber which functions to couple light between the fundamental mode propagating in the waveguide core and a guided cladding mode. Such gratings have an index modulation along the waveguiding axis of the fiber, and may be formed by writing with UV irradiation, etching, or other means of making periodic perturbations.
A Mach-Zehnder coupler device is a form of a Mach-Zehnder interferometer. In a Mach-Zehnder coupler device, a coupler splits light into two or more waveguides, typically optical fibers, which have different optical path lengths. A second coupler recombines this light after the light has traveled the different optical path lengths. In addition, Mach-Zehnder coupler devices may be used as demultiplexers and in sensor applications. Variations in the Mach-Zehnder coupler device family includes MultiClad.TM. Mach-Zehnder coupler devices, fused fiber Mach-Zehnder coupler devices and Mach-Zehnder lattice filters.
It has been found that the use of optical waveguide devices such as long period fiber gratings and Mach-Zehnder coupler devices is limited by their temperature dependence. In such devices, thermal spectral shifts of greater than 0.04 nm/.degree. C. at a transmitting wavelength of 1550 nm limit their application and usefulness in environments of differing temperature.